1. Technical Field of the Invention
This invention relates generally to computing and more particularly to storage of information.
2. Description of Related Art
Computing systems are known to communicate, process, and store data. Such computing systems range from wireless smart phones to data centers that support millions of web searches, stock trades, or on-line purchases every day. Computing processing is known to manipulate data from one form into another. For instance, raw picture data from an image sensor may be compressed, or manipulated, in accordance with a picture compression standard to produce a standardized compressed picture that can be saved or shared with others. Computer processing capability continues to advance as processing speed advances and software applications that perform the manipulation become more sophisticated.
With recent advances in computing processing speed and communication speed, computers may manipulate real time media from voice to streaming high definition (HD) video. Purpose-built communications devices, like the cell phone, are being replaced or augmented by more general-purpose information appliances. For example, smart phones can support telephony communications but they are also capable of text messaging, and accessing the internet to perform functions including email, web browsing, remote applications access, and media communications. Media communications may include telephony voice, image transfer, music files, video files, real time video streaming, and more.
Each type of computing system is constructed, and hence operates, in accordance with one or more communication, processing, and storage standards. With such standards, and with advances in technology, more and more of the global information content is being successfully converted into electronic formats and consumed by users in these electronic formats. For example, more digital cameras are now being sold than film cameras, thus producing more digital pictures that are shared and viewed electronically. High growth rates have consistently been observed for web-based programming. Web-based programming is electronically distributing among billions of users a large amount of content over the Internet and this content was, until recently, all broadcast by just a few entities over the air television stations and cable television providers. Digital content standards, such as used in pictures, papers, books, video entertainment, home video, all enable this global transformation to a digital format. Electronic content pervasiveness is producing increasing demands on the storage function of computing systems.
A typical computer storage function includes one or more memory devices that match the needs of the various operational aspects of the processing and communication functions. For example, a memory device may include solid-state NAND flash, random access memory (RAM), read only memory (ROM), a mechanical hard disk drive, or other types of storage. Each type of memory device has a particular performance range, use case, operational environment, and normalized cost. The computing system architecture optimizes the use of one or more types of memory devices to achieve the desired functional, cost, reliability, performance goals, etc. of the computing system. Generally, the immediacy of access dictates what type of memory device is used. For example, RAM memory can be accessed in any random order, all with a constant response time. By contrast, memory device technologies that require physical movement such as magnetic discs, tapes, and optical discs, have a variable response times as the physical movement can take longer than the data transfer, but often these devices can store larger volumes of data in a reliable manner, long-term manner.
Each type of computer storage system is constructed, and hence operates, in accordance with one or more storage standards. For instance, computer storage systems may operate in accordance with one or more standards including, but not limited to network file system (NFS), flash file system (FFS), disk file system (DFS), small computer system interface (SCSI), internet small computer system interface (iSCSI), file transfer protocol (FTP), and web-based distributed authoring and versioning (WebDAV). An operating systems (OS) and storage standard may specify the data storage format and interface between the processing subsystem and the memory devices. The interface may specify a structure, such as directories and files. Typically, a memory controller provides an interface function between the processing function and memory devices. As new storage systems are developed, the memory controller functional requirements may change to adapt to new standards.
Memory devices are subject to failure and will eventually fail, especially those memory devices that utilize technologies that require physical movement, like a disc drive. For example, it is not uncommon for a disc drive to suffer from bit level corruption on a regular basis, or suffer from a complete drive failure after an average of three years of use. One common solution is to utilize more costly disc drives that have higher quality internal components. Another solution is to utilize multiple levels of redundant disc drives to abate these issues by replicating the data into two or more copies. One such redundant drive approach is called redundant array of independent discs (RAID). Multiple physical discs comprise an array where parity data is added to the original data before storing the data across the array. The parity is calculated such that the failure of one or more discs will not result in the loss of the original data. The original data can be reconstructed from the other working discs if one or more discs fails. RAID 5 uses three or more discs to protect data from the failure of any one disc. The parity and redundancy overhead reduces the capacity of what three independent discs can store by one third (n−1=3−2=2 discs of capacity using 3 discs). RAID 6 can recover from a loss of two discs and requires a minimum of four discs with an efficiency of n−2. Typical RAID systems utilize a RAID control to encode and decode the data across the array.
The drawbacks of the RAID approach include effectiveness, efficiency, and security. As more discs are added, the probability of one or two discs failing rises and is not negligible, especially if the more-desirable and less-costly discs are used. When one disc fails, it should be immediately replaced and the data reconstructed before a second drive fails, whereby data full recovery is no longer an option. To provide high reliability over a long time period, it is also common to mirror RAID arrays at different physical locations, especially if the RAID array is part of a national level computing system with occasional site outages. Unauthorized file access becomes a more acute problem when whole copies of the same file are replicated in many locations/geographies, either on just one storage system site or at two or more sites. In light of the effectiveness, the efficiency of dedicating 1 to 2 discs per array for the RAID data-recovery overhead is an issue.
Therefore, a need exists to provide a data storage solution that provides more effective timeless continuity of data, minimizes adverse affects of multiple memory elements failures, provides improved security, can be adapted to a wide variety of storage system standards and is compatible with current and anticipated computing and communications systems.